Chapter 11 Biology 25: Human Biology Prof. Gonsalves Los Angeles City College Loosely Based on Mader’s Human Biology,7 th edition

Skeletal System Components: Bones, ligaments, and cartilage. Functions:  Along with muscular system:  Movement and locomotion.  Mechanical work: Lifting, pulling, pushing objects.  Body support.  Protection of delicate internal organs (brain, heart, lungs, etc.)  Calcium storage Homeostatic Role:  Helps maintain constant blood calcium levels.

Skeletal System: Protection, Movement, & Support

Connective Tissue Large amounts of extracellular (ECF) material in the spaces between connective tissue cells. Large amounts of extracellular (ECF) material in the spaces between connective tissue cells. 4 Types of Connective Tissue: 4 Types of Connective Tissue:  Connective tissue proper  Cartilage  Bone  Blood

Connective Tissue Proper Loose connective tissue: Loose connective tissue:  Scattered collagen and tissue fluid.  Dermis of skin Dense fibrous connective tissue: Dense fibrous connective tissue:  Regular arranged.  Collagen oriented in same direction. TendonsTendons  Irregularly arranged.  Resists forces applied in many directions. Capsules and sheathsCapsules and sheaths

Cartilage Chondrocytes. Chondrocytes. Supportive and protective tissue. Supportive and protective tissue. Elastic properties to tissues. Elastic properties to tissues. Precursor to many bones. Precursor to many bones. Articular surfaces on joints. Articular surfaces on joints.

Bone Hydroxyapatite crystals Hydroxyapatite crystals Osteoblasts: Osteoblasts:  Bone-forming cells Osteocytes: Osteocytes:  Trapped osteoblasts: less active Osteoclasts: Osteoclasts:  Bone resorbing cells

General Anatomy of a Long Bone Diaphysis - main shaft of the bone Diaphysis - main shaft of the bone Epiphysis - large end of the bone Epiphysis - large end of the bone Metaphysis - where above meet during bone growth Metaphysis - where above meet during bone growth Articular Cartilage - covers epiphysis, reduce friction Articular Cartilage - covers epiphysis, reduce friction Periosteum - dense, white covering around the bone Periosteum - dense, white covering around the bone  fibrous layer - blood, lymph, nerves pass through  osteogenic layer - where bone cells originate Medullary (marrow) Cavity - adults, yellow marrow Medullary (marrow) Cavity - adults, yellow marrow Endosteum - lines medullary cavity, houses bone cells Endosteum - lines medullary cavity, houses bone cells

Microanatomy of Compact (Dense) Bone General Features General Features  few empty spaces (dense)  thicker in diaphysis than epiphysis  concentric ring-like structure Osteon (Haversian System) - Components of Compact Bone Osteon (Haversian System) - Components of Compact Bone  central (Haversian) canal - vessels and nerves  osteocytes - mature bone cells (from osteoblasts)  lacunae - spaces where osteocytes reside  lamellae - rings around canal, house lacunae  canaliculi - projections from lacunae + osteocytes Supporting Structures Supporting Structures  perforating (Volkmann) canals - run perpendicular  interstitial lamellae - between osteons

Ossification: The Formation of Bone During Development Endochondral Ossification (replacing hyaline cartilage) Endochondral Ossification (replacing hyaline cartilage)  cartilage "bone model" formed in the embryo  perichondrium - membrane around the cartilage  vessel penetrates cartilage, brings osteoblasts  cartilage converted into compact bone  perichondrium --> periosteum  chondrocytes gradually hypertrophy and die  vessels move into space and convert to bone  primary ossification center - in diaphysis  secondary ossification center - in epiphysis  epiphyseal plate - between the two, still cartilage

Bone Remodeling - Spongy Bone Converted to Compact Bone osteoclasts - resorption of old bone tissue osteoclasts - resorption of old bone tissue  lysosome release of digestive enzymes  cell "phagocytoses" (engulfs) particles osteoblasts - lay down new bone in its place osteoblasts - lay down new bone in its place bone constantly undergoes remodeling throughout life bone constantly undergoes remodeling throughout life  Ca needed in muscle, nerve, blood clotting  fractures repaired immediately Factors essential for proper bone growth Factors essential for proper bone growth  Ca and P in proper amount in diet  trace amounts of Boron and Manganese  Vitamin D - regulates Ca metabolism  Vitamin C - maintenance of bone matrix  Vitamin A - osteoclast/blast function  Vitamin B12 - osteoblast function  Human Growth Hormone (HGH) - pituitary  Calcitonin - thyroid, Ca absorption to bone  Parathormone - parathyroid, Ca release to blood  Sex Hormones - Testosterone + Estrogen

Classification of Bones  Long Bones – considerably longer than wide; shaft with 2 ends (most limb bones, finger bones, etc.)  Short Bones – roughly cube shaped (wrist bones)  Sesamoid bone – short bone within a tendon (patella)  Flat bones – Flattened, thin, and usually curved (most cranial bones, ribs, sternum, and scapula)  Irregular bones – irregularly shaped (vertebrae, hip bones)

Bone Classification There are two divisions of the adult skeleton with a total of 206 bones There are two divisions of the adult skeleton with a total of 206 bones  Axial Skeleton includes 80 bones  Skull (22), middle ear ossicles (6), hyoid (1), vertebral column (26), and thorax (25)  Appendicular Skeleton includes 126 bones  Pectoral girdle (4), upper extremities (60), pelvic girdle (2), and lower extremities (60)

Synovial Joints Structure Structure  any joint where there is a space between bones  synovial cavity - space between the bones  freely moveable joints (diarthrotic)  articular cartilage - covers articular surface  articular capsule - encloses the cavity itself  fibrous capsule - attached to periosteum ligaments - clearly defined connectionsligaments - clearly defined connections  synovial membrane - inner layer of capsule produces synovial fluidproduces synovial fluid reduces friction in the jointreduces friction in the joint  accessory ligaments - additional support  extracapsular - outside capsule  intracapsular - within capsule  articular discs (menisci) - pads between bones  bursae - sac-like structures that reduce friction  between tendons, muscle, ligaments: and bone